The application of the siphon principle on a toilet to strengthen sewage suction is widely used. Under atmospheric pressure, the release of water from the water tank generates the siphon phenomenon that increases the efficiency of drainage. However, this siphon phenomenon requires a large amount of water to ensure proper drainage. In order to reduce water consumption, Chinese Patent Application No. 200410022242.7 discloses a suction-type water-saving toilet. The structure includes a piston tube at the end of the toilet siphon tube. The piston movement within the piston tube creates negative pressure at the end of the siphon tube. This causes the water in the pipeline to siphon rapidly, thereby decreasing water consumption. Due to the size limitation of the toilet itself, the installation location and the operational space are limited. In addition, the piston head exerts a large working stroke. To allow the piston head to complete an entire working stroke, a complex structure which includes pulling string, scroll and rod is used. This design in turn results in defects such as complexity in structure, difficulty in operation, and low efficiency, etc., and hence restricting the technology and general application of such “suction-type water-saving toilet”.